The present invention relates to video compression and decompression, and more particularly to transform methods such as DCT in block compression and decompression.
H.26L is a new video compression video standard being developed by ITU-T. It offers much higher coding efficiency which provides about 30–50% additional bit-rate reduction at the same coding qualities as compared to the MPEG-4 SP. A typical application of H.26L could be wireless video on demand, in which the bandwidth is so limited that a coding standard of high compression ratio is strongly desired.
As illustrated in FIG. 2, the basic coding techniques in H.26L are still the motion compensated prediction, transform, quantization and entropy coding. However, it differs from MPEG4/H.263 in great detail. One of major differences lies in the transform and quantization. Instead of 8×8 DCT transforms, H.26L uses a 4×4 integer transforms for the residual coding (residual blocks are generated by using the motion compensation for inter-coded macroblocks, and using the intra prediction for intra-coded macroblocks). Both the transform and quantization are designed for 32-arithmetic.
However, in the typical H.26L application, such as wireless video on demand, the hand-held devices are normally powered by 16-bit chipsets that are low-cost and have low power consumption. It is very expensive to implement 32-bit based transforms and quantization on 16-bit devices. Therefore, it is of interests to H.26L adoption that a 16-bit based transform and quantization is supported.